The invention relates to a safety ski binding comprising a releasable holding jaw, in particular front jaw, engaging one end of the ski boot and a counter jaw, in particular heel jaw, engaging the other end of the ski boot.
In a known safety ski binding of this type (DE-PS 3,015,478) provision is made for the resilient biasing between the lock member and the heel jaw housing to be present only in the rest position with the ski boot not inserted whilst said biasing, when the binding is attached is automatically cancelled in dependence upon a longitudinal displacement of the counter jaw housing in the longitudinal guide against the action of the thrust spring. The purpose of providing the resilient biasing only in the rest position is to avoid rattling of the binding during transport caused by play in the longitudinal guides whilst the play should be present when the ski boot is inserted in order to obstruct as little as possible the resilient relative movement of the counter jaw housing in the longitudinal guide when the binding is in use.
In such safety ski bindings the purpose of the thrust spring is of course to compensate spacing changes of the front and heel jaws on bending of the ski. If for example when passing through a trough the ski bends to a greater extent the distance between the front and heel jaws would change. In such a case the heel jaw may be displaced somewhat against the force of the thrust spring so that a constant distance is ensured between the two jaws of the safety ski binding.
However, the thrust spring also has a disadvantageous effect on the safety behaviour of the binding. The greater the thrust spring is compressed, which depends not only on the bending of the ski but also on the size of the inserted ski boot or on snow and ice intermediate layers, the greater the forwardly directed longitudinal force exerted by the thrust spring via the heel jaw and the ski boot on the front jaw. Since generally this longitudinal force influences the release behaviour of the preferably laterally, possibly also however upwardly, releasable front jaw considerably in the sense of making said release more difficult with increased longitudinal force, the aim will be to keep the thrust force as low as possible. However, to ensure reliable holding of the boot between front and heel jaws under all operating and weather conditions this force must not drop below a predetermined value.
The objective of the present invention is now to provide a safety ski binding of the type mentioned at the beginning in which the increase of the thrust force with increasingly compressed thrust spring no longer increases corresponding to the thereby increasing spring force but only to an appreciably lesser degree or even not at all.
The idea underlying the invention is also to be seen in that in each position of the heel jaw, i.e. in particular in all displacement positions during use of the binding with the ski boot inserted, the spreading force between the lock member and the heel jaw housing is derived from the thrust spring and is preferably proportional thereto. Accordingly, the clamping forces between the heel jaw housing and the longitudinal guides increase with increasing compression of the thrust spring and the frictional forces acting within the longitudinal guides thus also increase. These frictional forces in turn reduce the thrust force acting on the ski boot so that the objective of limiting the rise of the thrust force with increasing compression of the thrust spring or preventing said rise is achieved in extremely simple manner with minimum constructional expenditure. A further pushing back of the heel jaw under relatively large bending of the ski is not prevented by the increased frictional force within the longitudinal guides because the forces at the jaws of the safety ski binding produced by bending of the ski are so large that the frictional forces and the force of the thrust spring are negligible compared therewith.
In safety ski bindings operating with thrust spring there is always the problem of being able to insert the heel jaw axially to various boot sizes by temporary releasing of the lock member from the ski. Various solutions of how, by hand or by means of a tool, simultaneously the lock member can be released from the ski and the heel jaw housing can be shifted longitudinally into the desired position are provided. These solutions are also of significance independently of the spreading force generation according to the invention.